Formation Kinetics of Oil-Rich, Nonionic Microemulsions

The formation kinetics of oil-rich, nonionic microemulsions were investigated along different mixing pathways using a fast stopped-flow device in combination with the new high-flux small-angle neutron spectrometer D33 (ILL, Grenoble, France). While the kinetics along most pathways were too fast to be resolved, two processes could be detected mixing brine and the binary cyclohexane/C10E5 solution. Here, too, the formation of large water-in-oil droplets was found to be faster than 20 ms and therewith faster than the accessible dead time. However, subsequently, both the disintegration of the large water-in-oil droplets (600 Å) and the uptake of water by swollen micelles (50-60 Å) could be resolved. Both processes occur on the time scale of a second. Strikingly, the total internal interface forms faster than 20 ms and does not change over time.